1. Field of the Invention
The present invention relates to a treating method for coating material waste water.
2. Description of the Prior Art
It has so far been usual that a flocculant is added to coating material waste water discharged from coating plants and coating material production plants in order to separate and remove quickly and efficiently coating materials contained therein to thereby coagulate and separate (floating or settling) the coating materials to remove them and that this coagulated and separated waste water is then subjected to biological treatment under aerobic atmosphere. In biological treatment, however, microorganisms are limited in a decomposition capacity. Accordingly, various methods such as an ozone decomposition method, a Fenton method and UV irradiation method have so far been developed in order to convert contaminants contained in waste water into substances which are liable to be decomposed by microorganisms. For example, a treating method in which waste water containing organic substances is irradiated with a UV ray and/or a visible ray in the presence of a photooxidation catalyst to thereby oxidize and decompose the organic substances is disclosed in Japanese Patent Application Laid-Open No. 155308/1996, and a method in which organic substances in water are irradiated with a UV ray and a micro wave at the same time in the presence of a photooxidation catalyst to thereby oxidize and decompose the organic substances is disclosed in Japanese Patent Application Laid-Open No. 259620/2001. Further, a method in which organic substances are separated and removed by applying high voltage and emitting an electromagnetic wave of a high frequency is disclosed in Japanese Patent Application Laid-Open No. 263056/2000 (WO00/56663 and EP1138635), and a method in which nitrate nitrogen in water is irradiated with a micro wave in the presence of a specific solid catalyst to thereby remove the nitrate nitrogen is disclosed in Japanese Patent Application Laid-Open No. 336850/2002.
However, it is difficult to sufficiently decompose contaminants by these methods, and when the contaminants have a high concentration or a treating amount grows large, a UV ray is absorbed in organic substances, so that substances which are not decomposed are likely to remain in final treated water.
An object of the present invention is to provide a method for treating efficiently coating material waste water by converting scarcely decomposable substances contained in coating material waste water into easily decomposable substances.